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concrete; see 8.10.2.2 (2),
b) Dispersion length, ldisp over which the concrete stresses gradually disperse to a linear

distribution across the concrete section; see 8.10.2.2 (4),
c) Anchorage length, lbpd, over which the tendon force Fpd in the ultimate limit state is fully

anchored in the concrete; see 8.10.2.3 (4) and (5).

ldisp h Vpd
d Vpi

lpt A lpt lbpd
ldisp

A - Linear stress distribution in member cross-section

Figure 8.16: Transfer of prestress in pretensioned elements; length parameters

8.10.2.2 Transfer of prestress

(1) At release of tendons, the prestress may be assumed to be transferred to the concrete by a
constant bond stress fbpt, where:

fbpt = Kp1 K1 fctd(t) (8.15)

where: is a coefficient that takes into account the type of tendon and the bond situation at
Kp1
release
K1
ˆfctd(t) Kp1 = 2,7 for indented wires
Kp1 = 3,2 for 3 and 7-wire strands
= 1,0 for good bond conditions (see 8.4.2)

= 0,7 otherwise, unless a higher value can be justified with regard to special

circumstances in execution

is the design tensile value of strength at time of release; fctd(t) = Dct˜0,7˜fctm(t) / JC
(see also 3.1.2 (9) and 3.1.6 (2)P) ‰

Note: Values of Kp1 for types of tendons other than those given above may be used subject to a European
Technical Approval

(2) The basic value of the transmission length, lpt, is given by:

lpt = D1D2IVpm0/fbpt (8.16)

where:
D1 = 1,0 for gradual release
= 1,25 for sudden release
D2 = 0,25 for tendons with circular cross section
= 0,19 for 3 and 7-wire strands
I is the nominal diameter of tendon
Vpm0 is the tendon stress just after release

(3) The design value of the transmission length should be taken as the less favourable of two
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values, depending on the design situation:

lpt1 = 0,8 lpt (8.17)
or (8.18)

lpt2 = 1,2 lpt

Note: Normally the lower value is used for verifications of local stresses at release, the higher value for
ultimate limit states (shear, anchorage etc.).

(4) Concrete stresses may be assumed to have a linear distribution outside the dispersion
ˆlength, see Figure 8.16:‰

l disp l 2 d2 (8.19)
pt

(5) Alternative build-up of prestress may be assumed, if adequately justified and if the
transmission length is modified accordingly.

ˆ8.10.2.3 Anchorage of tendons for the ultimate limit state‰

(1) The anchorage of tendons should be checked in sections where the concrete tensile stress
exceeds fctk,0,05. The tendon force should be calculated for a cracked section, including the
ˆeffect of shear according to 6.2.3 (7); see also 9.2.1.3. Where the concrete tensile stress is less‰
than fctk,0,05, no anchorage check is necessary.

(2) The bond strength for anchorage in the ultimate limit state is:

fbpd = Kp2 K1 fctd (8.20)

where:

Kp2 is a coefficient that takes into account the type of tendon and the bond situation at
anchorage

Kp2 = 1,4 for indented wires or
Kp2 = 1,2 for 7-wire strands
K1 is as defined in 8.10.2.2 (1)

Note : Values of Kp2 for types of tendons other than those given above may be used subject to a European
Technical Approval.

(3) Due to increasing brittleness with higher concrete strength, fctk,0,05 should here be limited to
the value for C60/75, unless it can be verified that the average bond strength increases above
this limit.

(4) The total anchorage length for anchoring a tendon with stress Vpd is: (8.21)

lbpd = lpt2 + D2I(Vpd - Vpmf)/fbpd

where
lpt2 is the upper design value of transmission length, see 8.10.2.2 (3)
D2 as defined in 8.10.2.2 (2)
Vpd is the tendon stress corresponding to the force described in (1)
Vpmf is the prestress after all losses

(5) Tendon stresses in the anchorage zone are illustrated in Figure 8.17.
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A

Vpd
Vpi
Vp oo

(1) (2)

A - Tendon stress

l pt1 B - Distance from end
l pt2
B

l bpd

Figure 8.17: Stresses in the anchorage zone of pre-tensioned members:
(1) at release of tendons, (2) at ultimate limit state

(6) In case of combined ordinary and pre-tensioned reinforcement, the anchorage capacities of
each may be summed.

8.10.3 Anchorage zones of post-tensioned members

(1) The design of anchorage zones should be in accordance with the application rules given in
this clause and those in 6.5.3.

(2) When considering the effects of the prestress as a concentrated force on the anchorage
zone, the design value of the prestressing tendons should be in accordance with 2.4.2.2 (3) and
the lower characteristic tensile strength of the concrete should be used.

(3) The bearing stress behind anchorage plates should be checked in accordance with the
relevant European Technical Approval.

(4) Tensile forces due to concentrated forces should be assessed by a strut and tie model, or
other appropriate representation (see 6.5). Reinforcement should be detailed assuming that it
acts at its design strength. If the stress in this reinforcement is limited to 300 MPa no check of
crackwidths is necessary.

(5) As a simplification the prestressing force may be assumed to disperse at an angle of spread
2E (see Figure 8.18), starting at the end of the anchorage device, where E may be assumed to
be arc tan 2/3.

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Plan of flange

E = arc tan(2/3) = 33.7q

A - tendon

Figure 8.18: Dispersion of prestress

8.10.4 Anchorages and couplers for prestressing tendons

(1)P The anchorage devices used for post-tensioned tendons shall be in accordance with those
specified for the prestressing system, and the anchorage lengths in the case of pre-tensioned
tendons shall be such as to enable the full design strength of the tendons to be developed,
taking account of any repeated, rapidly changing action effects.

(2)P Where couplers are used they shall be in accordance with those specified for the
prestressing system and shall be so placed - taking account of the interference caused by these
devices - that they do not affect the bearing capacity of the member and that any temporary
anchorage which may be needed during construction can be introduced in a satisfactory
manner.

(3) Calculations for local effects in the concrete and for the transverse reinforcement should be
made in accordance with 6.5 and 8.10.3.

(4) In general, couplers should be located away from intermediate supports.

(5) The placing of couplers on 50% or more of the tendons at one cross-section should be
avoided unless it can be shown that a higher percentage will not cause more risk to the safety
of the structure.

8.10.5 Deviators

(1)P A deviator shall satisfy the following requirements:
- withstand both longitudinal and transverse forces that the tendon applies to it and transmit
these forces to the structure;
- ensure that the radius of curvature of the prestressing tendon does not cause any
overstressing or damage to it.

(2)P In the deviation zones the tubes forming the sheaths shall be able to sustain the radial
pressure and longitudinal movement of the prestressing tendon, without damage and without
impairing its proper functioning.

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(3)P The radius of curvature of the tendon in a deviation zone shall be in accordance with EN
10138 and appropriate European Technical Approvals.
(4) Designed tendon deviations up to an angle of 0,01 radians may be permitted without using
a deviator. The forces developed by the change of angle using a deviator in accordance with
the relevant European Technical Approval should be taken into account in the design
calculations.

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SECTION 9 DETAILING OF MEMBERS AND PARTICULAR RULES

9.1 General

(1)P The requirements for safety, serviceability and durability are satisfied by following the
rules given in this section in addition to the general rules given elsewhere.

(2) The detailing of members should be consistent with the design models adopted.

(3) Minimum areas of reinforcement are given in order to prevent a brittle failure, wide cracks
and also to resist forces arising from restrained actions.

Note: The rules given in this section are mainly applicable to reinforced concrete buildings.

9.2 Beams

9.2.1 Longitudinal reinforcement

9.2.1.1 Minimum and maximum reinforcement areas

(1) The area of longitudinal tension reinforcement should not be taken as less than As,min.

Note 1: See also 7.3 for area of longitudinal tension reinforcement to control cracking.

Note 2: The value of As,min for beams for use in a Country may be found in its National Annex. The
recommended value is given in the following:

As,min = 0,26 fctm bt d but not less than 0,0013btd (9.1N)
fyk

Where:

bt denotes the mean width of the tension zone; for a T-beam with the flange in compression, only the
width of the web is taken into account in calculating the value of bt.

fctm should be determined with respect to the relevant strength class according to Table 3.1.

Alternatively, for secondary elements, where some risk of brittle failure may be accepted, As,min may be taken
as 1,2 times the area required in ULS verification.

(2) Sections containing less reinforcement than As,min should be considered as unreinforced
(see Section 12).

(3) The cross-sectional area of tension or compression reinforcement should not exceed As,max
outside lap locations.

Note: The value of As,max for beams for use in a Country may be found in its National Annex. The
recommended value is 0,04Ac.

(4) For members prestressed with permanently unbonded tendons or with external prestressing
cables, it should be verified that the ultimate bending capacity is larger than the flexural
cracking moment. A capacity of 1,15 times the cracking moment is sufficient.

9.2.1.2 Other detailing arrangements

(1) In monolithic construction, even when simple supports have been assumed in design, the
section at supports should be designed for a bending moment arising from partial fixity of at

least E1 of the maximum bending moment in the span.

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Note 1: The value of E1 for beams for use in a Country may be found in its National Annex. The

recommended value is 0,15.

Note 2: The minimum area of longitudinal reinforcement section defined in 9.2.1.1 (1) applies.

(2) At intermediate supports of continuous beams, the total area of tension reinforcement As of
a flanged cross-section should be spread over the effective width of flange (see 5.3.2). Part of it
may be concentrated over the web width (See Figure 9.1).

beff
As

beff1 hf
bw beff2

Figure 9.1: Placing of tension reinforcement in flanged cross-section.

(3) Any compression longitudinal reinforcement (diameter I) which is included in the resistance
calculation should be held by transverse reinforcement with spacing not greater than 15I.

9.2.1.3 Curtailment of longitudinal tension reinforcement

(1) Sufficient reinforcement should be provided at all sections to resist the envelope of the
acting tensile force, including the effect of inclined cracks in webs and flanges.

(2) For members with shear reinforcement the additional tensile force, 'Ftd, should be
calculated according to 6.2.3 (7). For members without shear reinforcement 'Ftd may be
estimated by shifting the moment curve a distance al = d according to 6.2.2 (5). This "shift rule"
may also be used as an alternative for members with shear reinforcement, where:

al = z (cot T - cot D)/2 (symbols defined in 6.2.3) (9.2)
The additional tensile force is illustrated in Figure 9.2.

(3) The resistance of bars within their anchorage lengths may be taken into account, assuming
a linear variation of force, see Figure 9.2. As a conservative simplification this contribution may
be ignored.

(4) The anchorage length of a bent-up bar which contributes to the resistance to shear should
be not less than 1,3 lbd in the tension zone and 0,7 lbd in the compression zone. It is measured
from the point of intersection of the axes of the bent-up bar and the longitudinal reinforcement.

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A lbd
lbd
B
C lbd

al 'Ftd

lbd al
'Ftd

lbd lbd
lbd
lbd

A - Envelope of MEd/z + NEd B - acting tensile force Fs C - resisting tensile force FRs

Figure 9.2: Illustration of the curtailment of longitudinal reinforcement, taking into
account the effect of inclined cracks and the resistance of
reinforcement within anchorage lengths

9.2.1.4 Anchorage of bottom reinforcement at an end supports

(1) The area of bottom reinforcement provided at ˆend‰ supports with little or no end fixity
assumed in design, should be at least E2 of the area of steel provided in the span.

Note: The value of E2 for beams for use in a Country may be found in its National Annex. The recommended

value is 0,25.

(2) The tensile force to be anchored may be determined according to ˆ 6.2.3 (7) ‰
(memberswith shear reinforcement) including the contribution of the axial force if any, or
according to the shift rule:

ˆFEd = |VEd| . al / z + NEd ‰ (9.3)

where NEd is the axial force, to be added to or subtracted from the tensile force; al see
9.2.1.3 (2).

(3) The anchorage length is lbd according to 8.4.4, measured from the line of contact between
beam and support. Transverse pressure may be taken into account for direct support. See
Figure 9.3.

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lbd

l bd

b

a) Direct support: Beam supported by b) Indirect support: Beam intersecting another

wall or column supporting beam

Figure 9.3: Anchorage of bottom reinforcement at end supports

9.2.1.5 Anchorage of bottom reinforcement at intermediate supports

(1) The area of reinforcement given in 9.2.1.4 (1) applies.

(2) The anchorage length should not be less than 10I (for straight bars) or not less than the
diameter of the mandrel (for hooks and bends with bar diameters at least equal to 16 mm) or

twice the diameter of the mandrel (in other cases) (see Figure 9.4 (a)). These minimum values

are normally valid but a more refined analysis may be carried out in accordance with 6.6.

(3) The reinforcement required to resist possible positive moments (e.g. settlement of the
support, explosion, etc.) should be specified in contract documents. This reinforcement should
be continuous which may be achieved by means of lapped bars (see Figure 9.4 (b) or (c)).

l lbd bd

dm I I
l t dm
l t 10I l t 10I

a) b) c)
Figure 9.4: Anchorage at intermediate supports

9.2.2 Shear reinforcement

(1) The shear reinforcement should form an angle D of between 45° and 90° to the longitudinal
axis of the structural element.

(2) The shear reinforcement may consist of a combination of:
- links enclosing the longitudinal tension reinforcement and the compression zone (see
Figure 9.5);
- bent-up bars;

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- cages, ladders, etc. which are cast in without enclosing the longitudinal reinforcement but
are properly anchored in the compression and tension zones.

A
B

A Inner link alternatives B Enclosing link

Figure 9.5: Examples of shear reinforcement

(3) Links should be effectively anchored. A lap joint on the leg near the surface of the web is
permitted provided that the link is not required to resist torsion.

(4) At least E3 of the necessary shear reinforcement should be in the form of links.

Note: The value of E3 for use in a Country may be found in its National Annex. The recommended value is 0, 5.
(5) The ratio of shear reinforcement is given by Expression (9.4):

Uw = Asw / (s . bw . sinD) (9.4)

where:

Uw is the shear reinforcement ratio
Uw should not be less than Uw,min

Asw is the area of shear reinforcement within length s
s is the spacing of the shear reinforcement measured along the longitudinal axis of

the member
bw is the breadth of the web of the member
D is the angle between shear reinforcement and the longitudinal axis (see 9.2.2 (1))

Note: The value of Uw,min for beams for use in a Country may be found in its National Annex. The
recommended value is given Expression (9.5N)

Uw,min = (0,08 fck ) /fyk (9.5N)

(6) The maximum longitudinal spacing between shear assemblies should not exceed sl,max.

Note: The value of sl,max for use in a Country may be found in its National Annex. The recommended value is
given by Expression (9.6N)

sl,max = 0,75d (1 + cot D ) (9.6N)
where D is the inclination of the shear reinforcement to the longitudinal axis of the beam.

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(7) The maximum longitudinal spacing of bent-up bars should not exceed sb,max:

Note: The value of sb,max for use in a Country may be found in its National Annex. The recommended value is
given by Expression (9.7N)

sb,max = 0,6 d (1 + cot D) (9.7N)

(8) The transverse spacing of the legs in a series of shear links should not exceed :st,max

Note: The value of st,max for use in a Country may be found in its National Annex. The recommended value is
given by Expression (9.8N)

st,max = 0,75d d 600 mm (9.8N)

9.2.3 Torsion reinforcement

(1) The torsion links should be closed and be anchored by means of laps or hooked ends, see
Figure 9.6, and should form an angle of 90° with the axis of the structural element.

or

a1) a2) a3)

a) recommended shapes b) not recommended shape

Note: The second alternative for a2) (lower sketch) should have a full lap length along the top.

Figure 9.6: Examples of shapes for torsion links

(2) The provisions of 9.2.2 (5) and (6) are generally sufficient to provide the minimum torsion
links required.

(3) The longitudinal spacing of the torsion links should not exceed u / 8 (see 6.3.2, Figure 6.11,
for the notation), or the requirement in 9.2.2 (6) or the lesser dimension of the beam cross-
section.

(4) The longitudinal bars should be so arranged that there is at least one bar at each corner,
the others being distributed uniformly around the inner periphery of the links, with a spacing not
greater than 350 mm.

9.2.4 Surface reinforcement

(1) It may be necessary to provide surface reinforcement either to control cracking or to ensure
adequate resistance to spalling of the cover.

ŠNote: Guidance on surface reinforcements is given in Informative Annex J.‹

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9.2.5 Indirect supports

(1) Where a beam is supported by a beam instead of a wall or column, reinforcement should
be provided and designed to resist the mutual reaction. This reinforcement is in addition to that
required for other reasons. This rule also applies to a slab not supported at the top of a beam.

(2) The supporting reinforcement between two beams should consist of links surrounding the
principal reinforcement of the supporting member. Some of these links may be distributed
outside the volume of the concrete, which is common to the two beams, (see Figure 9.7).

B

d h2 /3 d h2 /2

d h1 /3 A
d h1 /2

A supporting beam with height h1 B supported beam with height h2 (h1 t h2)

Figure 9.7: Placing of supporting reinforcement in the intersection zone of two
beams (plan view)

9.3 Solid slabs

(1) This section applies to one-way and two-way solid slabs for which b and leff are not less
than 5h (see 5.3.1).

9.3.1 Flexural reinforcement

9.3.1.1 General

(1) For the minimum and the maximum steel percentages in the main direction 9.2.1.1 (1) and
(3) apply.

Note: In addition to Note 2 of 9.2.1.1 (1), for slabs where the risk of brittle failure is small, As,min may be taken
as 1,2 times the area required in ULS verification.

(2) Secondary transverse reinforcement of not less than 20% of the principal reinforcement
should be provided in one way slabs. In areas near supports transverse reinforcement to
principal top bars is not necessary where there is no transverse bending moment.

(3) The spacing of bars should not exceed smax,slabs.

Note; The value of smax,slabs for use in a Country may be found in its National Annex. The recommended value
is:

- for the principal reinforcement, 3h d 400 mm, where h is the total depth of the slab;

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- for the secondary reinforcement, 3,5h d 450 mm .
In areas with concentrated loads or areas of maximum moment those provisions become respectively:
- for the principal reinforcement, 2h d 250 mm
- for the secondary reinforcement, 3h d 400 mm.

(4) The rules given in 9.2.1.3 (1) to (3), 9.2.1.4 (1) to (3) and 9.2.1.5 (1) to (2) also apply but
with al = d.

9.3.1.2 Reinforcement in slabs near supports

(1) In simply supported slabs, half the calculated span reinforcement should continue up to the
support and be anchored therein in accordance with 8.4.4.

Note: Curtailment and anchorage of reinforcement may be carried out according to 9.2.1.3, 9.2.1.4 and
9.2.1.5.

(2) Where partial fixity occurs along an edge of a slab, but is not taken into account in the
analysis, the top reinforcement should be capable of resisting at least 25% of the maximum
moment in the adjacent span. This reinforcement should extend at least 0,2 times the length of
the adjacent span, measured from the face of the support. It should be continuous across
internal supports and anchored at end supports. At an end support the moment to be resisted
may be reduced to 15% of the maximum moment in the adjacent span.

9.3.1.3 Corner reinforcement

(1) If the detailing arrangements at a support are such that lifting of the slab at a corner is
restrained, suitable reinforcement should be provided.

9.3.1.4 Reinforcement at the free edges

(1) Along a free (unsupported) edge, a slab should normally contain longitudinal and transverse
reinforcement, generally arranged as shown in Figure 9.8.

(2) The normal reinforcement provided for a slab may act as edge reinforcement.

h

t 2h

Figure 9.8: Edge reinforcement for a slab

9.3.2 Shear reinforcement

(1) A slab in which shear reinforcement is provided should have a depth of at least 200 mm.

(2) In detailing the shear reinforcement, the minimum value and definition of reinforcement ratio
in 9.2.2 apply, unless modified by the following.

(3) In slabs, if |VEd| d 1/3 VRd,max, (see 6.2), the shear reinforcement may consist entirely of
bent-up bars or of shear reinforcement assemblies.

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(4) The maximum longitudinal spacing of successive series of links is given by: (9.9)
smax = 0,75d(1+cotD )
where D is the inclination of the shear reinforcement.

The maximum longitudinal spacing of bent-up bars is given by: (9.10)
smax = d.

(5) The maximum transverse spacing of shear reinforcement should not exceed 1,5d.

9.4 Flat slabs

9.4.1 Slab at internal columns

(1) The arrangement of reinforcement in flat slab construction should reflect the behaviour
under working conditions. In general this will result in a concentration of reinforcement over the
columns.

(2) At internal columns, unless rigorous serviceability calculations are carried out, top
reinforcement of area 0,5 At should be placed in a width equal to the sum of 0,125 times the
panel width on either side of the column. At represents the area of reinforcement required to
resist the full negative moment from the sum of the two half panels each side of the column.

(3) Bottom reinforcement (t 2 bars) in each orthogonal direction should be provided at internal
columns and this reinforcement should pass through the column.

9.4.2 Slab at edge and corner columns

(1) Reinforcement perpendicular to a free edge required to transmit bending moments from the

slab to an edge or corner column should be placed within the effective width be shown in Figure
9.9.

cz cz

A A

cy
y y cy

be = cz + y z A
be = z + y/2
A Slab edge

Note: y can be > cy Note: z can be > cz and y can be > cy

a) Edge column b) Corner column

Note: y is the distance from the edge of the slab to the innermost face of the column.

Figure 9.9: Effective width, be, of a flat slab

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9.4.3 Punching shear reinforcement

(1) Where punching shear reinforcement is required (see 6.4) it should be placed between the
loaded area/column and kd inside the control perimeter at which shear reinforcement is no
longer required. It should be provided in at least two perimeters of link legs (see Figure 9.10).
The spacing of the link leg perimeters should not exceed 0,75d.

The spacing of link legs around a perimeter should not exceed 1,5d within the first control
perimeter (2d from loaded area), and should not exceed 2d for perimeters outside the first
control perimeter where that part of the perimeter is assumed to contribute to the shear capacity
(see Figure 6.22).

For bent down bars as arranged in Figure 9.10 b) one perimeter of link legs may be considered
sufficient.

AB d
0,25d
d kd

! 0,3d

d 0,75d

A - outer control perimeter requiring A
shear reinforcement
< 0,5d

B - first control perimeter not requiring # 2d
shear reinforcement

a) Spacing of links b) Spacing of bent-up bars

Figure 9.10: Punching shear reinforcement

Note: See 6.4.5 (4) for the value of k.

(2) Where shear reinforcement is required the area of a link leg (or equivalent), Asw,min, is given
by Expression (9.11).

ŠAsw,min ˜ (1,5˜sinD + cosD)/(sr˜ st) ≥ ⋅ f FN ‹ (9.11)
f \N

where :

D is the angle between the shear reinforcement and the main steel (i.e. for vertical links

D = 90° and sin D = 1)

sr is the spacing of shear links in the radial direction
st is the spacing of shear links in the tangential direction
fck is in MPa

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The vertical component of only those prestressing tendons passing within a distance of 0.5d of
the column may be included in the shear calculation.

(3) Bent-up bars passing through the loaded area or at a distance not exceeding 0,25d from
this area may be used as punching shear reinforcement (see Figure 9.10 b), top).

(4) The distance between the face of a support, or the circumference of a loaded area, and the
nearest shear reinforcement taken into account in the design should not exceed d/2. This
distance should be taken at the level of the tensile reinforcement. If only a single line of bent-up
bars is provided, their slope may be reduced to 30°.

9.5 Columns

9.5.1 General

(1) This clause deals with columns for which the larger dimension h is not greater than 4 times
the smaller dimension b.

9.5.2 Longitudinal reinforcement

(1) Longitudinal bars should have a diameter of not less than I min.

Note: The value of I min for use in a Country may be found in its National Annex. The recommended value is
8 mm.

(2) The total amount of longitudinal reinforcement should not be less than As,min.

Note: The value of As,min for use in a Country may be found in its National Annex. The recommended value is
given by Expression (9.12N)

As,min 0,10 NEd or 0,002 Ac whichever is the greater (9.12N)
fyd

where:

fyd is the design yield strength of the reinforcement
NEd is the design axial compression force

(3) The area of longitudinal reinforcement should not exceed As,max.

Note: The value of As,max for use in a Country may be found in its National Annex. The recommended value is
0,04 Ac outside lap locations unless it can be shown that the integrity of concrete is not affected, and that the
full strength is achieved at ULS. This limit should be increased to 0,08 Ac at laps.

(4) For columns having a polygonal cross-section, at least one bar should be placed at each
corner. The number of longitudinal bars in a circular column should not be less than four.

9.5.3 Transverse reinforcement

(1) The diameter of the transverse reinforcement (links, loops or helical spiral reinforcement)
should not be less than 6 mm or one quarter of the maximum diameter of the longitudinal bars,
whichever is the greater. The diameter of the wires of welded mesh fabric for transverse
reinforcement should not be less than 5 mm.

(2) The transverse reinforcement should be anchored adequately.

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(3) The spacing of the transverse reinforcement along the column should not exceed scl,tmax

Note: The value of scl,tmax for use in a Country may be found in its National Annex. The recommended value is
the least of the following three distances:
- 20 times the minimum diameter of the longitudinal bars
- the lesser dimension of the column
- 400 mm

(4) The maximum spacing required in (3) should be reduced by a factor 0,6:

(i) in sections within a distance equal to the larger dimension of the column cross-section
above or below a beam or slab;

(ii) near lapped joints, if the maximum diameter of the longitudinal bars is greater than 14
mm. A minimum of 3 bars evenly placed in the lap length is required.

(5) Where the direction of the longitudinal bars changes, (e.g. at changes in column size), the
spacing of transverse reinforcement should be calculated, taking account of the lateral forces
involved. These effects may be ignored if the change of direction is less than or equal to 1 in 12.

(6) Every longitudinal bar or bundle of bars placed in a corner should be held by transverse
reinforcement. No bar within a compression zone should be further than 150 mm from a
restrained bar.

9.6 Walls

9.6.1 General

(1) This clause refers to reinforced concrete walls with a length to thickness ratio of 4 or more
and in which the reinforcement is taken into account in the strength analysis. The amount and
proper detailing of reinforcement may be derived from a strut-and-tie model (see 6.5). For walls
subjected predominantly to out-of-plane bending the rules for slabs apply (see 9.3).

9.6.2 Vertical reinforcement

(1) The area of the vertical reinforcement should lie between As,vmin and As,vmax.

Note 1: The value of As,vmin for use in a Country may be found in its National Annex. The recommended value
is 0,002 Ac.

Note 2: The value of As,vmax for use in a Country may be found in its National Annex. The recommended value
is 0,04 Ac outside lap locations unless it can be shown that the concrete integrity is not affected and that the
full strength is achieved at ULS. This limit may be doubled at laps.

(2) Where the minimum area of reinforcement, ,As,vmin controls in design, half of this area should
be located at each face.

(3) The distance between two adjacent vertical bars shall not exceed 3 times the wall thickness
or 400 mm whichever is the lesser.

9.6.3 Horizontal reinforcement

(1) Horizontal reinforcement running parallel to the faces of the wall (and to the free edges)
should be provided at each surface. It should not be less than As,hmin.

Note: The value of As,hmin for use in a Country may be found in its National Annex. The recommended value is
either 25% of the vertical reinforcement or 0,001 Ac, whichever is greater.

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(2) The spacing between two adjacent horizontal bars should not be greater than 400 mm.

9.6.4 Transverse reinforcement

(1) In any part of a wall where the total area of the vertical reinforcement in the two faces
exceeds 0,02 Ac, transverse reinforcement in the form of links should be provided in
accordance with the requirements for columns (see 9.5.3). The large dimension referred to in
9.5.3 (4) (i) need not be taken greater than 4 x thickness of wall.

(2) Where the main reinforcement is placed nearest to the wall faces, transverse reinforcement
should also be provided in the form of links with at least of 4 per m2 of wall area.

Note: Transverse reinforcement need not be provided where welded wire mesh and bars of diameter I d 16

mm are used with concrete cover larger than 2I ,

9.7 Deep beams

(1) Deep beams (for definition see 5.3.1 (3)) should normally be provided with an orthogonal
reinforcement mesh near each face, with a minimum of As,dbmin.

ŠNote: The value of As,dbmin for use in a Country may be found in its National Annex. The recommended value
is 0,001A c but not less than 150 mm²/m in each face and each direction.‹

(2) The distance between two adjacent bars of the mesh should not exceed the lesser of twice
the deep beam thickness or 300 mm.

(3) Reinforcement, corresponding to the ties considered in the design model, should be fully
anchored for equilibrium in the node, see 6.5.4, by bending the bars, by using U-hoops or by
anchorage devices, unless a sufficient length is available between the node and the end of the
beam permitting an anchorage length of lbd.

9.8 Foundations

9.8.1 Pile caps

(1) The distance from the outer edge of the pile to the edge of the pile cap should be such that
the tie forces in the pile cap can be properly anchored. The expected deviation of the pile on
site should be taken into account.

(2) Reinforcement in a pile cap should be calculated either by using strut-and-tie or flexural
methods as appropriate.

(3) The main tensile reinforcement to resist the action effects should be concentrated in the
stress zones between the tops of the piles. A minimum bar diameter I min should be provided.
If the area of this reinforcement is at least equal to the minimum reinforcement, evenly
distributed bars along the bottom surface of the member may be omitted. Also the sides and the
top surface of the member may be unreinforced if there is no risk of tension developing in these
parts of the member.

Note: The value of I min for use in a Country may be found in its National Annex. The recommended value is
8 mm.

(4) Welded transverse bars may be used for the anchorage of the tension reinforcement. In this
case the transverse bar may be considered to be part of the transverse reinforcement in the
anchorage zone of the reinforcement bar considered.
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(5) The compression caused by the support reaction from the pile may be assumed to spread
at 45 degree angles from the edge of the pile (see Figure 9.11). This compression may be
taken into account when calculating the anchorage length.

A 45 A - compressed area

50 mm

Figure 9.11: Compressed area increasing the anchorage capacity
9.8.2 Column and wall footings
9.8.2.1 General
(1) The main reinforcement should be anchored in accordance with the requirements of 8.4
and 8.5. A minimum bar diameter I min should be provided. In footings the design model shown in
ˆ9.8.2.2‰ may be used.

Note: The value of I min for use in a Country may be found in its National Annex. The recommended value is
8 mm.

(2) The main reinforcement of circular footings may be orthogonal and concentrated in the
middle of the footing for a width of 50% r 10% of the diameter of the footing, see Figure 9.12. In
this case the unreinforced parts of the element should be considered as plain concrete for
design purposes.

0,5 B
B

Figure 9.12: Orthogonal reinforcement in circular spread footing on soil
(3) If the action effects cause tension at the upper surface of the footing, the resulting tensile
stresses should be checked and reinforced as necessary.

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9.8.2.2 Anchorage of bars

(1) The tensile force in the reinforcement is determined from equilibrium conditions, taking into
account the effect of inclined cracks, see Figure 9.13. The tensile force Fs at a location x should
be anchored in the concrete within the same distance x from the edge of the footing.

ze NEd dh
Fs b

e
Fc
Fs,max zi

A lb B
x

R

Figure 9.13: Model for tensile force with regard to inclined cracks
(2) The tensile force to be anchored is given by:

Fs = R ˜ ze/zi (9.13)

where:
R is the resultant of ground pressure within distance x
ze is the external lever arm, i.e. distance between R and the vertical force NEd
NEd is the vertical force corresponding to total ground pressure between sections A and
B
zi is the internal lever arm, i.e. distance between the reinforcement and the horizontal
force Fc
Fc is the compressive force corresponding to maximum tensile force Fs,max

(3) Lever arms ze and zi may be determined with regard to the necessary compression zones
for NEd and Fc respectively. As simplifications, ze may be determined assuming e = 0,15b, see
Figure 9.13 and zi may be taken as 0,9d.

(4) The available anchorage length for straight bars is denoted lb in Figure 9.13. If this length is
not sufficient to anchor Fs, bars may either be bent up to increase the available length or be
provided with end anchorage devices.

(5) For straight bars without end anchorage the minimum value of x is the most critical. As a
simplification xmin = h/2 may be assumed. For other types of anchorage, higher values of x may
be more critical.

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9.8.3 Tie beams

(1) Tie beams may be used to eliminate the eccentricity of loading of the foundations. The
beams should be designed to resist the resulting bending moments and shear forces. A
minimum bar diameter I min for the reinforcement resisting bending moments should be provided.

Note: The value of I min for use in a Country may be found in its National Annex. The recommended value is
8 mm.

(2) Tie beams should also be designed for a minimum downward load of q1 if the action of
compaction machinery can cause effects to the tie beams.

Note: The value of q1 for use in a Country may be found in its National Annex. The recommended value is
10 kN/m.

9.8.4 Column footing on rock

(1) Adequate transverse reinforcement should be provided to resist the splitting forces in the
footing, when the ground pressure in the ultimate states exceeds q2. This reinforcement may be
distributed uniformly in the direction of the splitting force over the height h (see Figure 9.14). A

minimum bar diameter, I min, should be provided.

Note: The values of q2 and of I min for use in a Country may be found in its National Annex. The
recommended values of q2 is 5 MPa and of I min is 8 mm.

(2) The splitting force, Fs, may be calculated as follows (see Figure 9.14) :

Fs = 0,25 (1 - c /h)NEd (9.14)

Where h is the lesser of b and H

b
c

NEd

b h
c H

b
NEd

H

H

a) footing with h t H b) section c) footing with h < H

Figure 9.14: Splitting reinforcement in footing on rock

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9.8.5 Bored piles

(1) The following clauses apply for reinforced bored piles. For unreinforced bored piles see
Section 12.

(2) In order to allow the free flow of concrete around the reinforcement it is of primary
importance that reinforcement, reinforcement cages and any attached inserts are detailed such
that the flow of concrete is not adversely affected.
ˆ(3) Bored piles should be provided with a minimum longitudinal reinforcement As,bpmin related
to pile cross section Ac.

Note: The values of As,bpmin and the associated Ac for use in a country may be found in its national annex.
The recommended values are given in Table 9.6N. This reinforcement should be distributed along
the periphery of the section.‰

Table 9.6N: Recommended minimum longitudinal reinforcement area in cast-in-place bored piles

Pile cross-section: Ac Minimum area of longitudinal
reinforcement: AS,bpmin
Ac d 0,5 m²
0,5 m² Ac d 1,0 m² AS t 0,005 ˜ Ac
AS t 25 cm2
Ac ! 1,0 m²
AS t 0,0025 ˜ Ac

The minimum diameter for the longitudinal bars should not be less than 16 mm. Piles should have at least 6
longitudinal bars. The clear distance between bars should not exceed 200 mm measured along the periphery
of the pile.

(4) For the detailing of longitudinal and transverse reinforcement in bored piles, see EN 1536.

9.9 Regions with discontinuity in geometry or action

(1) D-regions should normally be designed with strut-and-tie models according to section 6.5
and detailed according to the rules given in Section 8.

Note: Further information is given in Annex J.

(2)P The reinforcement, corresponding to the ties, shall be fully anchored by an anchorage of
lbd according to 8.4.

9.10 Tying systems

9.10.1 General

(1)P Structures which are not designed to withstand accidental actions shall have a suitable
tying system, to prevent progressive collapse by providing alternative load paths after local
damage. The following simple rules are deemed to satisfy this requirement.

(2) The following ties should be provided:
a) peripheral ties
b) internal ties
c) horizontal column or wall ties
d) where required, vertical ties, particularly in panel buildings.

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(3) Where a building is divided by expansion joints into structurally independent sections, each
section should have an independent tying system.

(4) In the design of the ties the reinforcement may be assumed to be acting at its characteristic
strength and capable of carrying tensile forces defined in the following clauses.

(5) Reinforcement provided for other purposes in columns, walls, beams and floors may be
regarded as providing part of or the whole of these ties.

9.10.2 Proportioning of ties

9.10.2 .1 General

(1) Ties are intended as a minimum and not as an additional reinforcement to that required by
structural analysis.

9.10.2.2 Peripheral ties

(1) At each floor and roof level an effectively continuous peripheral tie within 1,2 m from the
edge should be provided. The tie may include reinforcement used as part of the internal tie.

(2) The peripheral tie should be capable of resisting a tensile force:

ˆFtie,per = li˜ q1 8 Q2 ‰ (9.15)

where:
Ftie,per tie force (here: tension)
li length of the end-span

ˆNote: Values of q1 and Q2 for use in a Country may be found in its National Annex. The recommended value of
q1 is 10 kN/m and of Q2 is 70 kN.‰

(3) Structures with internal edges (e.g. atriums, courtyards, etc.) should have peripheral ties in
the same way as external edges which shall be fully anchored.

9.10.2.3 Internal ties

(1) These ties should be at each floor and roof level in two directions approximately at right
angles. They should be effectively continuous throughout their length and should be anchored
to the peripheral ties at each end, unless continuing as horizontal ties to columns or walls.

(2) The internal ties may, in whole or in part, be spread evenly in the slabs or may be grouped
at or in beams, walls or other appropriate positions. In walls they should be within 0,5 m from
the top or bottom of floor slabs, see Figure 9.15.

(3) In each direction, internal ties should be capable of resisting a design value of tensile force
Ftie,int (in kN per metre width):

Note: Values of Ftie,int for use in a Country may be found in its National Annex. The recommended value is 20
kN/m.

(4) In floors without screeds where ties cannot be distributed across the span direction, the
transverse ties may be grouped along the beam lines. In this case the minimum force on an
internal beam line is:

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ˆFtie = q3 ջ (l1 + l2)/ 2 Š• Q4 ‹‰ (9.16)

where:
l1, l2 are the span lengths (in m) of the floor slabs on either side of the beam (see Figure

9.15)

Š Note: Values of q3 and Q4 for use in a Country may be found in its National Annex. The recommended value
of q3 is 20 kN/m and of Q4 is 70 kN.‹

(5) Internal ties should be connected to peripheral ties such that the transfer of forces is
assured.

A

l2

B l1

A - peripheral tie B - internal tie C
C - horizontal column or wall tie

Figure 9.15: Ties for Accidental Actions

9.10.2.4 Horizontal ties to columns and/or walls

(1) Edge columns and walls should be tied horizontally to the structure at each floor and roof
level.

(2) The ties should be capable of resisting a tensile force ftie,fac per metre of the façade. For
columns the force need not exceed Ftie,col.

Note: Values of ftie,fac and Ftie,col for use in a Country may be found in its National Annex. The recommended
value of ftie,fac is 20 kN/m and of Ftie,col is 150 kN.

(3) Corner columns should be tied in two directions. Steel provided for the peripheral tie may be
used as the horizontal tie in this case.

9.10.2.5 Vertical ties

(1) In panel buildings of 5 storeys or more, vertical ties should be provided in columns and/or
walls to limit the damage of collapse of a floor in the case of accidental loss of the column or
wall below. These ties should form part of a bridging system to span over the damaged area.

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(2) Normally, continuous vertical ties should be provided from the lowest to the highest level,
capable of carrying the load in the accidental design situation, acting on the floor above the
column/wall accidentally lost. Other solutions e.g. based on the diaphragm action of remaining
wall elements and/or on membrane action in floors, may be used if equilibrium and sufficient
deformation capacity can be verified.
(3) Where a column or wall is supported at its lowest level by an element other than a
foundation (e.g. beam or flat slab) accidental loss of this element should be considered in the
design and a suitable alternative load path should be provided.
9.10.3 Continuity and anchorage of ties
(1)P Ties in two horizontal directions shall be effectively continuous and anchored at the
perimeter of the structure.
(2) Ties may be provided wholly within the insitu concrete topping or at connections of precast
members. Where ties are not continuous in one plane, the bending effects resulting from the
eccentricities should be considered.
(3) Ties should not normally be lapped in narrow joints between precast units. Mechanical
anchorage should be used in these cases.

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SECTION 10 ADDITIONAL RULES FOR PRECAST CONCRETE ELEMENTS AND
STRUCTURES

10.1 General

(1)P The rules in this section apply to buildings made partly or entirely of precast concrete
elements, and are supplementary to the rules in other sections. Additional matters related to
detailing, production and assembly are covered by specific product standards.

Note: Headings are numbered 10 followed by the number of the corresponding main section. Headings of
lower level are numbered consecutively, without connection to sub-headings in previous sections.

10.1.1 Special terms used in this section

Precast element: element manufactured in a factory or a place other than the final position in
the structure, protected from adverse weather conditions

Precast product: precast element manufactured in compliance with a specific CEN standard

Composite element: element comprising in-situ and precast concrete with or without
reinforcement connectors

Rib and block floor: consists of precast ribs (or beams) with an infill between them, made of
blocks, hollow clay pots or other forms of permanent shuttering, with or without an in-situ
topping

Diaphragm: plane member which is subjected to in-plane forces; may consist of several precast
units connected together

Tie: in the context of precast structures, a ties is a tensile member, effectively continuous,
placed in a floor, wall or column

Isolated precast member: member for which, in case of failure, no secondary means of load
transfer is available

Transient situation in precast concrete construction includes
- demoulding
- transport to the storage yard
- storage (support and load conditions)
- transport to site
- erection (hoisting)
- construction (assembly)

10.2 Basis of design, fundamental requirements

(1)P In design and detailing of precast concrete elements and structures, the following shall be
considered specifically:

- transient situations (see 10.1.1)
- bearings; temporary and permanent
- connections and joints between elements

(2) Where relevant, dynamic effects in transient situations should be taken into account. In the
absence of an accurate analysis, static effects may be multiplied by an appropriate factor (see
also product standards for specific types of precast products).
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(3) Where required, mechanical devices should be detailed in order to allow ease of assembly,
inspection and replacement.

10.3 Materials

10.3.1 Concrete

10.3.1.1 Strength

(1) For precast products in continuous production, subjected to an appropriate quality control
system according to the product standards, with the concrete tensile strength tested, a
statistical analysis of test results may be used as a basis for the evaluation of the tensile
strength that is used for serviceability limit states verifications, as an alternative to Table 3.1.

(2) Intermediate strength classes within Table 3.1 may be used.

(3) In the case of heat curing of precast concrete elements, the compressive strength of
ˆconcrete at an age t before 28 days, fcm(t), may be estimated from Expression (3.1) in which the‰

concrete age t is substituted by the temperature adjusted concrete age obtained by Expression

(B.10) of Annex B.

Note: The coefficient Ecc(t) should be limited to 1.

For the effect of heat curing Expression (10.1) may be used:

fcm(t ) fcmp fcm fcmp 1) log(t tp 1) (10.1)
log(28 tp

Where fcmp is the mean compressive strength after the heat curing (i.e. at the release of the
prestress), measured by testing of samples at the time tp (tp < t), that went through the same
heat treatment with the precast elements.

10.3.1.2 Creep and shrinkage

(1) In the case of a heat curing of the precast concrete elements, it is permitted to estimate the
values of creep deformations according to the maturity function, Expression (B.10) of Annex B.

(2) In order to calculate the creep deformations, the age of concrete at loading t0 (in days) in
Expression (B.5) should be replaced by the equivalent concrete age obtained by Expressions
(B.9) and (B.10) of Annex B.

(3) In precast elements subjected to heat curing it may be assumed that:
a) the shrinkage strain is not significant during heat curing and
b) autogenous shrinkage strain is negligible.

10.3.2 Prestressing steel

ˆ10.3.2.1 Technological properties of prestressing steel‰

(1)P For pre-tensioned members, the effect on the relaxation losses of increasing the
temperature while curing the concrete, shall be considered.

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Note: The relaxation is accelerated during the application of a thermal curing when a thermal strain is
introduced at the same time. Finally, the relaxation rate is reduced at the end of the treatment.

(2) An equivalent time teq should be added to the time after tensioning t in the relaxation time
functions, given in 3.3.2(7), to cater for the effects of the heat treatment on the prestress loss
due to the relaxation of the prestressing steel. The equivalent time can be estimated from
Expression (10.2):

1,14Tmax 20 n
Tmax 20
teq ¦
T ǻ ti 20 ǻ ti (10.2)
i1

where is the equivalent time (in hours)
teq is the temperature (in °C) during the time interval 'ti
is the maximum temperature (in °C) during the heat treatment
T('ti)
Tmax

10.5 Structural analysis

10.5.1 General

(1)P The analysis shall account for:
- the behaviour of the structural units at all stages of construction using the appropriate
geometry and properties for each stage, and their interaction with other elements (e.g.
composite action with in-situ concrete, other precast units);
- the behaviour of the structural system influenced by the behaviour of the connections
between elements, with particular regard to actual deformations and strength of
connections;
- the uncertainties influencing restraints and force transmission between elements arising
from deviations in geometry and in the positioning of units and bearings.

(2) Beneficial effects of horizontal restraint caused by friction due to the weight of any
supported element may only be used in non seismic zones (using JG,inf) and where:

- the friction is not solely relied upon for overall stability of the structure;
- the bearing arrangements preclude the possibility of accumulation of irreversible sliding of

the elements, such as caused by uneven behaviour under alternate actions (e.g. cyclic
thermal effects on the contact edges of simply supported elements);
- the possibility of significant impact loading is eliminated

(3) The effects of horizontal movements should be considered in design with respect to the
resistance of the structure and the integrity of the connections.

10.5.2 Losses of prestress

(1) In the case of heat curing of precast concrete elements, the lessening of the tension in the

tendons and the restrained dilatation of the concrete due to the temperature, induce a specific
thermal loss 'PT. This loss may be estimated by the Expression (10.3):

ǻ Pș 0,5 A p Ep D c (Tmax To ) (10.3)

Where is the cross-section of tendons
Ap is the elasticity modulus of tendons
E

p

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ˆDC is the linear coefficient of thermal expansion for concrete (see 3.1.3(5))‰
Tmax T0 is the difference between the maximum and initial temperature in the concrete
near the tendons, in °C

Note: Any loss of prestress, 'PT, caused by elongation due to heat curing may be ignored if preheating of the
tendons is applied.

10.9 Particular rules for design and detailing

10.9.1 Restraining moments in slabs

(1) Restraining moments may be resisted by top reinforcement placed in the topping or in plugs
in open cores of hollow core units. In the former case the horizontal shear in the connection
should be checked according to 6.2.5. In the latter case the transfer of force between the in situ
concrete plug and the hollow core unit should be verified according to 6.2.5. The length of the
top reinforcement should be in accordance with 9.2.1.3.

(2) Unintended restraining effects at the supports of simply supported slabs should be
considered by special reinforcement and/or detailing.

10.9.2 Wall to floor connections

(1) In wall elements installed over floor slabs, reinforcement should normally be provided for
possible eccentricities and concentrations of the vertical load at the end of the wall. For floor
elements see 10.9.1 (2).

(2) No specific reinforcement is required provided the vertical load per unit length is d 0,5h.fcd,
where h is the wall thickness, see Figure 10.1. The load may be increased to 0,6h.fcd with
reinforcement according to Figure 10.1, having diameter I t 6 mm and spacing s not greater
than the lesser of h and 200 mm. For higher loads, reinforcement should be designed according
to (1). A separate check should be made for the lower wall.

h s
I

Figure 10.1: Example of reinforcement in a wall over a connection between two
floor slabs.

10.9.3 Floor systems

(1)P The detailing of floor systems shall be consistent with assumptions in analysis and design.
Relevant product standards shall be considered.

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(2)P Where transverse load distribution between adjacent units has been taken into account,
appropriate shear connection shall be provided.

(3)P The effects of possible restraints of precast units shall be considered, even if simple
supports have been assumed in design.

(4) Shear transfer in connections may be achieved in different ways. Three main types of
connections shown in Figure 10.2.

(5) Transverse distribution of loads should be based on analysis or tests, taking into account
possible load variations between precast elements. The resulting shear force between floor
units should be considered in the design of connections and adjacent parts of elements (e.g.
outside ribs or webs).

For floors with uniformly distributed load, and in the absence of a more accurate analysis, this
shear force per unit length may be taken as:

vEd = qEd˜be/3 (10.4)

where: is the design value of variable load (kN/m2)
qEd is the width of the element
be

a) concreted or grouted b) welded or bolted c) reinforced topping.
connections connections (this shows (vertical reinforcement
one type of welded connectors to topping may
connection as an be required to ensure
example) shear transfer at ULS)

Figure 10.2: Examples of connections for shear transfer

(6) Where precast floors are assumed to act as diaphragms to transfer horizontal loads to
bracing units, the following should be considered:

- the diaphragm should form part of a realistic structural model, taking into account the
deformation compatibility with bracing units,

- the effects of horizontal deformations should be taken into account for all parts of the
structure involved in the transfer of horizontal loads,

- the diaphragm should be reinforced for the tensile forces assumed in the structural
model,

- stress concentrations at openings and connections should be taken into account in the
detailing of reinforcement.

(7) Transverse reinforcement for shear transfer across connections in the diaphragm may be
concentrated along supports, forming ties consistent with the structural model. This
reinforcement may be placed in the topping, if it exists.

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(8) Precast units with a topping of at least 40 mm may be designed as composite members, if
shear in the interface is verified according to 6.2.5. The precast unit should be checked at all
stages of construction, before and after composite action has become effective.

(9) Transverse reinforcement for bending and other action effects may lie entirely within the
topping. The detailing should be consistent with the structural model, e.g. if two-way spanning is
assumed.

(10) Webs or ribs in isolated slab units (i.e. units which are not connected for shear transfer)
should be provided with shear reinforcement as for beams.

(11) Floors with precast ribs and blocks without topping may be analysed as solid slabs, if the
insitu transverse ribs are provided with continuous reinforcement through the precast
longitudinal ribs and at a spacing sT according to Table 10.1.

(12) In diaphragm action between precast slab elements with concreted or grouted
connections, the average longitudinal shear stress vRdi should be limited to 0,1 MPa for very
smooth surfaces, and to 0,15 MPa for smooth and rough surfaces. See 6.2.5 for definition of
surfaces.

Table 10.1: Maximum spacing of transverse ribs, sT for the analysis of floors with
ribs and block as solid slabs. sL = spacing of longitudinal ribs, lL =
length (span) of longitudinal ribs, h = thickness of ribbed floor

Type of imposed loading sL d lL/8 sL > lL/8
Residential, snow not required sT d 12 h
Other sT d 8 h
sT d 10 h

10.9.4 Connections and supports for precast elements

10.9.4.1 Materials

(1)P Materials used for connections shall be:
- stable and durable for the design working life of the structure
- chemically and physically compatible
- protected against adverse chemical and physical influences
- fire resistant to match the fire resistance of the structure.

(2)P Supporting pads shall have strength and deformation properties in accordance with the
design assumptions.

(3)P Metal fastenings for claddings, other than in environmental classes X0 and XC1 (Table
4.1) and not protected against the environment, shall be of corrosion resistant material. If
inspection is possible, coated material may also be used.

(4)P Before undertaking welding, annealing or cold forming the suitability of the material shall
be verified.

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10.9.4.2 General rules for design and detailing of connections

(1)P Connections shall be able to resist action effects consistent with design assumptions, to
accommodate the necessary deformations and ensure robust behaviour of the structure.

(2)P Premature splitting or spalling of concrete at the ends of elements shall be prevented,
taking into account

- relative movements between elements
- deviations
- assembly requirements
- ease of execution
- ease of inspection

(3) Verification of resistance and stiffness of connections may be based on analysis, possibly
assisted by testing (for design assisted by testing, see EN 1990, Annex D). Imperfections
should be taken into account. Design values based on tests should allow for unfavourable
deviations from testing conditions.

10.9.4.3 Connections transmitting compressive forces

(1) Shear forces may be ignored in compression connections if they are less than 10% of the
compressive force.

(2) For connections with bedding materials like mortar, concrete or polymers, relative
movement between the connected surfaces should be prevented during hardening of the
material.

(3) Connections without bedding material (dry connections) should only be used where an

appropriate quality of workmanship can be achieved. The average bearing stress between
plane surfaces should not exceed 0,3 fcd. Dry connections including curved (convex) surfaces
should be designed with due consideration of the geometry.

(4) Transverse tensile stresses in adjacent elements should be considered. They may be due
to concentrated compression according to Figure 10.3a, or to the expansion of soft padding
according to Figure 10.3b. Reinforcement in case a) may be designed and located according to
6.5. Reinforcement in case b) should be placed close to the surfaces of the adjacent elements.

(5) In the absence of more accurate models, reinforcement in case b) may be calculated in
accordance with Expression (10.5):

As = 0,25 (t / h) FEd / fyd (10.5)

where:
As is the reinforcement area in each surface
t is the thickness of padding
h is the dimension of padding in direction of reinforcement
FEd is the compressive force in connection.

(6) The maximum capacity of compression connections can be determined according to 6.7, or
can be based on analysis, possibly assisted by testing (for design assisted testing, see EN
1990).

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a) Concentrated bearing b) Expansion of soft padding

Figure 10.3: Transverse tensile stresses at compression connections.

10.9.4.4 Connections transmitting shear forces

(1) For shear transfer in interfaces between two concretes, e.g. a precast element and in situ
concrete, see 6.2.5.

10.9.4.5 Connections transmitting bending moments or tensile forces

(1)P Reinforcement shall be continuous across the connection and anchored in the adjacent
elements.

(2) Continuity may be obtained by, for example
- lapping of bars
- grouting of reinforcement into holes
- overlapping reinforcement loops
- welding of bars or steel plates
- prestressing
- mechanical devices (threaded or filled sleeves)
- swaged connectors (compressed sleeves)

10.9.4.6 Half joints

(1) Half joints may be designed using strut-and-tie models according to 6.5. Two alternative
models and reinforcements are indicated in Figure 10.4. The two models may be combined.

Note: The figure shows only the main features of strut-and-tie models.

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Figure 10.4: Indicative models for reinforcement in half joints.
10.9.4.7 Anchorage of reinforcement at supports

(1) Reinforcement in supporting and supported members should be detailed to ensure
anchorage in the respective node, allowing for deviations. An example is shown in Figure 10.5.

The effective bearing length a1 is controlled by a distance d (see Figure 10.5) from the edge of
the respective elements where:

di = ci + 'ai with horizontal loops or otherwise end anchored bars

di = ci + 'ai + ri with vertically bent bars

Where
ci is concrete cover
'ai is a deviation (see 10.9.5.2 (1)
ri is the bend radius

See Figure 10.5 and 10.9.5.2 (1) for definitions of 'a2 or 'a3.

d2 > a1 + 'a3 c3

r3

r2
c2 > a1 + 'a2 d3

Figure 10.5: Example of detailing of reinforcement in support

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10.9.5 Bearings

10.9.5.1 General

(1)P The proper functioning of bearings shall be ensured by reinforcement in adjacent
members, limitation of bearing stress and measures to account for movement or restraint.

(2)P For bearings which do not permit sliding or rotation without significant restraint, actions
due to creep, shrinkage, temperature, misalignment, lack of plumb etc. shall be taken into
account in the design of adjacent members.

(3) The effects of (2)P may require transverse reinforcement in supporting and supported
members, and/or continuity reinforcement for tying elements together. They may also influence
the design of main reinforcement in such members.

(4)P Bearings shall be designed and detailed to ensure correct positioning, taking into account
production and assembling deviations.

(5)P Possible effects of prestressing anchorages and their recesses shall be taken into
account.

10.9.5.2 Bearings for connected (non-isolated) members

(1) The nominal length a of a simple bearing as shown in Figure 10.6 may be calculated as:

a = a1 + a2 + a3 + 'a22 'a32 (10.6)

where:
a1 is the net bearing length with regard to bearing stress, a1 = FEd / (b1 fRd), but not

less than minimum values in Table 10.2
FEd is the design value of support reaction
b1 is the net bearing width, see (3)
fRd is the design value of bearing strength, see (2)
a2 is the distance assumed ineffective beyond outer end of supporting member, see

Figure 10.6 and Table 10.3
a3 is the similar distance for supported member, see Figure 10.6 and Table 10.4

b
1

a a
1 1

a3+ 'a3 a a2+ 'a2

Figure 10.6: Example of bearing with definitions.

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'a2 is an allowance for deviations for the distance between supporting members, see
Table 10.5
'a3 is an allowance for deviations for the length of the supported member, 'a3 =
ln/2500, ln is length of member.

Table 10.2: Minimum value of a1 in mm

Relative bearing stress, VEd / fcd d 0,15 0,15 - 0,4 > 0,4

Line supports (floors, roofs) 25 30 40

Ribbed floors and purlins 55 70 80

Concentrated supports (beams) 90 110 140

Table 10.3: Distance a2 (mm) assumed ineffective from outer end of supporting
member. Concrete padstone should be used in cases (-)

Š d 0,15 0,15 - 0,4 > 0,4

Support material and type VEd / fcd 0 0 10
5 10 15
Steel line 5 10 15
10 15 25
concentrated 10 15 25
20 25 35
Reinforced line 10 15 (-)
20 25 (-)
concrete t C30/37 concentrated

Plain concrete and line

rein. concrete < C30/37concentrated

Brickwork line

concentrated ‹

Table 10.4: Distance a3 (mm) assumed ineffective beyond outer end of supported
member

Detailing of reinforcement Support

Line Concentrated

Continuous bars over support 00
(restrained or not)
Straight bars, horizontal loops, close to 5 15, but not less
end of member than end cover
Tendons or straight bars
exposed at end of member 5 15
Vertical loop reinforcement
15 end cover + inner
radius of bending

Table 10.5: Allowance 'a2 for deviations for the clear distance between the faces
of the supports. l = span length

Support material 'a2
Steel or precast concrete 10 d l/1200 d 30 mm
Brickwork or cast in-situ concrete 15 d l/1200 + 5 d 40 mm

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(2) In the absence of other specifications, the following values can be used for the bearing
strength:

fRd = 0,4 fcd for dry connections (see 10.9.4.3 (3) for definition)

fRd = fbed d 0,85 fcd for all other cases

where
fcd is the the lower of the design strengths for supported and supporting member
fbed is the design strength of bedding material

(3) If measures are taken to obtain a uniform distribution of the bearing pressure, e.g. with
mortar, neoprene or similar pads, the design bearing width b1 may be taken as the actual width
of the bearing. Otherwise, and in the absence of a more accurate analysis, b1 should not be

greater than to 600 mm.

10.9.5.3 Bearings for isolated members

(1)P The nominal length shall be 20 mm greater than for non-isolated members.

(2)P If the bearing allows movements in the support, the net bearing length shall be increased
to cover possible movements.

(3)P If a member is tied other than at the level of its bearing, the net bearing length a1 shall be
increased to cover the effect of possible rotation around the tie.

10.9.6 Pocket foundations

10.9.6.1 General

(1)P Concrete pockets shall be capable of transferring vertical actions, bending moments and
horizontal shears from columns to the soil. The pocket shall be large enough to enable a good
concrete filling below and around the column.

10.9.6.2 Pockets with keyed surfaces

(1) Pockets expressly wrought with indentations or keys may be considered to act
monolithically with the column.

(2) Where vertical tension due to moment transfer occurs careful detailing of the overlap
reinforcement of the similarly wrought column and the foundation is needed, allowing for the
ˆseparation of the lapped bars. The lap length according to 8.7 should be increased by at least ‰
the horizontal distance between bars in the column and in the foundation (see Figure 10.7 (a) )
Adequate horizontal reinforcement for the lapped splice should be provided.

(3) The punching shear design should be as for monolithic column/foundation connections
according to 6.4, as shown in Figure 10.7 (a), provided the shear transfer between the column
and footing is verified. Otherwise the punching shear design should be as for pockets with
smooth surfaces.

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10.9.6.3 Pockets with smooth surfaces

(1) The forces and the moment may be assumed to be transferred from column to foundation
by compressive forces F1, F2 and F3 through the concrete filling and corresponding friction

forces, as shown in Figure 10.7 (b). This model requires
l t 1,2 h.

Fv h 0,1l
M F
s Fh
Mv
ls
Fh

l PF2 PF1 F1
0,1l PF3
F2

s
F3

(a) with keyed joint surface (b) with smooth joint surface
Figure 10.7: Pocket Foundations

(2) The coefficient of friction should not be taken greater than P = 0,3.

(3) Special attention should be paid to:
- detailing of reinforcement for F1 in top of pocket walls
- transfer of F1 along the lateral walls to the footing
- anchorage of main reinforcement in the column and pocket walls
- shear resistance of column within the pocket
- punching resistance of the footing slab under the column force, the calculation for which may
take into account the insitu structural concrete placed under the precast element.

10.9.7 Tying systems

(1) For plate elements loaded in their own plane, e.g. in walls and floor diaphragms, the
necessary interaction may be obtained by tying the structure together with peripheral and/or
internal ties.

The same ties may also act to prevent progressive collapse according to 9.10.

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SECTION 11 LIGHTWEIGHT AGGREGATE CONCRETE STRUCTURES
11.1 General

(1)P This section provides additional requirements for lightweight aggregate concrete (LWAC).
Reference is made to the other Sections (1 to 10 and 12) of this document and the Annexes.

Note. Headings are numbered 11 followed by the number of the corresponding main section. Headings of
lower level are numbered consecutively, without connection to sub-headings in previous sections. If
alternatives are given for Expressions, Figures or Tables in the other sections, the original reference numbers
are also prefixed by 11.

11.1.1 Scope

(1)P All clauses of the Sections 1 to 10 and 12 are generally applicable, unless they are
substituted by special clauses given in this section. In general, where strength values
originating from Table 3.1 are used in Expressions, those values have to be replaced by the
corresponding values for lightweight concrete, given in this section in Table 11.3.1.

(2)P Section 11 applies to all concretes with closed structure made with natural or artificial
mineral lightweight aggregates, unless reliable experience indicates that provisions different
from those given can be adopted safely.

(3) This section does not apply to aerated concrete either autoclaved or normally cured nor
lightweight aggregate concrete with an open structure.

(4)P Lightweight aggregate concrete is concrete having a closed structure and a density of not
more than 2200 kg/m3 consisting of or containing a proportion of artificial or natural lightweight
aggregates having a particle density of less than 2000 kg/m3

11.1.2 Special symbols

1(P) The following symbols are used specially for lightweight concrete:

LC the strength classes of lightweight aggregate concrete are preceded by the symbol LC
KE is a conversion factor for calculating the modulus of elasticity
K1 is a coefficient for determining tensile strength
K2 is a coefficient for determining creep coefficient
K3 is a coefficient for determining drying shrinkage
U is the oven-dry density of lightweight aggregate concrete in kg/m3

For the mechanical properties an additional subscript l (lightweight) is used.

11.2 Basis of design

1(P) Section 2 is valid for lightweight concrete without modifications.

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11.3 Materials

11.3.1 Concrete
(1)P In EN 206-1 lightweight aggregate ˆconcrete‰ is classified according to its density
as shown in Table 11.1. In addition this table gives corresponding densities for plain and
reinforced concrete with normal percentages of reinforcement which may be used for design
purposes in calculating self-weight or imposed permanent loading. Alternatively, the density may
be specified as a taget value.

(2) Alternatively the contribution of the reinforcement to the density may be determined by
calculation.

Table 11.1: Density classes and corresponding design densities of LWAC
according to EN 206-1

Density class 1,0 1,2 1,4 1,6 1,8 2,0
Density (kg/m3)
801- 1001- 1201- 1401- 1601- 1801-
Density Plain concrete 1000 1200 1400 1600 1800 2000
(kg/m3) Reinforced concrete 1050 1250 1450 1650 1850 2050
1150 1350 1550 1750 1950 2150

(3) The tensile strength of lightweight aggregate concrete may be obtained by multiplying the fct
values given in Table 3.1 by a coefficient:

K1 = 0,40 + 0,60U /2200 (11.1)

where
ŠU is the upper limit of the oven dry density for the relevant class in accordance with Table 11.1‹

11.3.2 Elastic deformation

(1) An estimate of the mean values of the secant modulus Elcm for LWAC may be obtained by
multiplying the values in Table 3.1, for normal density concrete, by the following coefficient:

KE = (U/2200)2 (11.2)

where U denotes the oven-dry density in accordance with EN 206-1 Section 4 (see Table
11.1).

Where accurate data are needed, e.g. where deflections are of great importance, tests should
be carried out in order to determine the Elcm values in accordance with ISO 6784.

Note: A Country’s National Annex may refer to non-contradictory complementary information.

(2) The coefficient of thermal expansion of LWAC depends mainly on the type of aggregate
used and varies over a wide range between about 4˜10-6 and 14˜10-6/K

For design purposes where thermal expansion is of no great importance, the coefficient of
thermal expansion may be taken as 8˜10-6/K.

The differences between the coefficients of thermal expansion of steel and lightweight
aggregate concrete need not be considered in design.

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Strength classes for light weight concrete Analytical
relation/Explanation
BS EN 1992-1-1:2004
EN 1992-1-1:2004 (E)flck (MPa) 12 16 20 253035 40 45 505560 70 80
Table 11.3.1: Stress and deformation characteristics for lightweight concrete
flck,cube 13 18 22 28 33 38 44 50 55 60 66 77 88
N3843 48 53 5863
(MPa)187
flctm = fctm ˜ K1
flcm 17 22 28 33 68 78 88 For flck t 20 MPa
(MPa)
flcm = flck + 8 (MPa)

flctm K1=0,40+0,60 /2200
(MPa)

flctk,0,05 Škf lcm (Ecm⋅ηE)‹ flctk,0,05 = fctk,0,05 ˜ K1 5% - fractile
(MPa) flctk,0,95 = fctk,0,95 ˜K1 95% - fractile
flctk,0,95 KE = ( /2200)2
(MPa) Elcm = Ecm ˜ KE see Figure 3.2

Elcm k = 1,1 for sanded lightweight aggregate concrete see Figure 3.2
(GPa ) k = 1,0 for all lightweight aggregate concrete
Hlc1 (‰)
lc1
Hlcu1(‰)

Hlc2 (‰) 2,0 2,2 2,3 2,4 2,5 see Figure 3.3

Hlcu2 (‰) 3,5 K1 3,1 1 2,9 1 2,7 1 2,6 1 see Figure 3.3
n 2,0
1,75 1,6 1,45 1,4 ˆ |Hlcu2| t |Hlc2| ‰

Hlc3(‰) 1,75 1,8 1,9 2,0 2,2 see Figure 3.4
Hlcu3(‰) 3,5 K1
3,1 1 2.9 1 2.7 1 2,6 1 see Figure 3.4

|Hlcu3| t |Hlc3|

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11.3.3 Creep and shrinkage

(1) For lightweight aggregate concrete the creep coefficient M may be assumed equal to the
value of normal density concrete multiplied by a factor (U /2200)2.

The creep strains so derived should be multiplied by a factor, K2, given by

K2 = 1,3 for flck d LC16/18
= 1,0 for flck t LC20/22

(2) The final drying shrinkage values for lightweight concrete can be obtained by multiplying the
values for normal density concrete in Table 3.2 by a factor, K3, given by

K3 = 1,5 for flck d LC16/18
= 1,2 for flck t LC20/22

(3) The Expressions (3.11), (3.12) and (3.13), which provide information for autogenous
shrinkage, give maximum values for lightweight aggregate concretes, where no supply of water
from the aggregate to the drying microstructure is possible. If water-saturated, or even partially
saturated lightweight aggregate is used, the autogenous shrinkage values will be considerably
reduced.

11.3.4 Stress-strain relations for non-linear structural analysis

(1) For lightweight aggregate concrete the values Hc1 and Hcu1 given in Figure 3.2 should be
substituted by H lc1 and H lcu1 given in Table 11.3.1.

11.3.5 Design compressive and tensile strengths

(1)P The value of the design compressive strength is defined as

ˆflcd = Dlcc flck / J C (11.3.15)

where JC is the partial safety factor for concrete, see Š2.4.2.4‹, and Dlcc is a coefficient
according to 3.1.6 (1)P.‰

Note: The value of Dlcc for use in a Country may be found in its National Annex. The recommended value is
0,85.

(2)P The value of the design tensile strength is defined as

Šflctd = Dlct flctk /γC (11.3.16)

where γC is the partial safety factor for concrete, see 2.4.2.4 and Dlct is a coefficient according
to 3.1.6 (2)P.‹

Note: The value of Dlct for use in a Country may be found in its National Annex. The recommended value is

0,85.

11.3.6 Stress-strain relations for the design of sections

(1) For lightweight aggregate concrete the values Hc2 and Hcu2 given in Figure 3.3 should be
replaced with the values of Hlc2 and Hlcu2 given in Table 11.3.1.

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(2) For lightweight aggregate concrete the values Hc3 and Hcu3 given in Figure 3.4 should be
replaced with the values of Hlc3 and Hlcu3 given in Table 11.3.1.

11.3.7 Confined concrete

(1) If more precise data are not available, the stress-strain relation shown in Figure 3.6 may be
used, with increased characteristic strength and strains according to:

flck,c = flck (1,0 + kV2/flck) (11.3.24)

Note: The value of k for use in a Country may be found in its National Annex. The recommended value is:
1,1 for lightweight aggregate concrete with sand as the fine aggregate
1,0 for lightweight aggregate (both fine and coarse aggregate) concrete

Hlc2,c = Hlc2 (flckc/flck)2 (11.3.26)
Hlcu2,c = Hlcu2 + 0,2V2/flck (11.3.27)

where Hlc2 and Hlcu2 follow from Table 11.3.1.

11.4 Durability and cover to reinforcement

11.4.1 Environmental conditions

(1) For lightweight aggregate concrete in Table 4.1 the same indicative exposure classes can
be used as for normal density concrete.

11.4.2 Concrete cover and properties of concrete

(1)P For lightweight aggregate concrete the values of minimum concrete cover given in
Table 4.2 shall be increased by 5 mm.

11.5 Structural analysis

11.5.1 Rotational capacity

ˆNote: For light weight concrete the value of T pl,d as shown in Figure 5.6N, should be multiplied by a factor
Hlcu2/H cu2.‰

11.6 Ultimate limit states

11.6.1 Members not requiring design shear reinforcement

(1) The design value of the shear resistance of a lightweight concrete member without shear
reinforcement VlRd,c follows from:

ˆVlRd,c = [ClRd,cK1k(100U l flck)1/3 + k1Vcp] bwd t (K1 vl,min + k1Vcp)bwd ‰ (11.6.2)

Šwhere K1 is defined in Expression (11.1), flck is taken from Table 11.3.1 and Vcp is the mean
compressive stress in the section due to axial force and prestress, where σcp<0.2 fcd .‹

Note: The values of ClRd,c, vl,min and k1 for use in a Country may be found in its National Annex. The
ˆrecommended value for ClRd,c is 0,15/JC, for vl,min is 0,028 k3/2fck1/2 and that for k1 is 0,15.‰

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ˆTable 11.6.1N: Values of vl,min for given values of d and flck ‰

vl,min (MPa)

d ˆf lck(MPa)‰
(mm)
20 30 40 50 60 70 80
200
400 0.36 0.44 0.50 0.56 0.61 0.65 0.70
600 0.29 0.35 0.39 0.44 0.48 0.52 0.55
800 0.25 0.31 0.35 0.39 0.42 0.46 0.49
• 1000 ˆ0.23‰ 0.28 0.32 0.36 0.39 0.42 0.45
0.22 0.27 0.31 0.34 0.37 0.40 0.43

(2) The shear force, VEd, calculated without reduction E (see 6.2.2 (6) should always satisfy the
condition:

ŠVEd = 0,5 bw d ν1 flcd (11.6.5)

where

νl is in accordance with 11.6.2. (1) ‹

11.6.2 Members requiring design shear reinforcement

(1) The reduction factor for the crushing resistance of the concrete struts is Q.1.
l

Note 1: The value ofν l for use in a Country may be found in its National Annex. The recommended value follows

from: (11.6.6N)

ˆν l = 0,5 (1- flck /250)‰

Š Note 2: For lightweight concrete ν l should not be modified in accordance with Note 2 of 6..2.3(3).‹

11.6.3 Torsion

11.6.3.1 Design procedure

(1) In Expression (6.30) for lightweight concrete Q is taken equal to Q1 according to 11.6.2 (1).
11.6.4 Punching

11.6.4.1 Punching shear resistance of slabs or column bases without shear
reinforcement

(1) The punching shear resistance per unit area of a lightweight concrete slab follows from

vlRd,c = ClRd,c k K1(100Ul flck )1/3 + k2 Vcp t (K1vl,min + k2Vcp) (11.6.47)

where
K1 is defined in Expression (11.1)
ClRd,c see 11.6.1 (1)
vl,min see 11.6.1 (1)

Note: The value k2 for use in a Country may be found in its National Annex. The recommended value is 0,08

Š(2) The punching shear resistance, v lRd, of lightweight concrete column bases follows from ‹

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vlRd,c = ClRd,c K1k (100Ul flck)1/3 2d/a t K1 vlmin˜2d/a (11.6.50)

where

K1 is defined in Expression (11.1)
ˆUl t 0,005‰

ClRd,c see 11.6.1 (1)
vl,min see 11.6.1 (1)

11.6.4.2 Punching shear resistance of slabs or column bases with shear reinforcement

(1) Where shear reinforcement is required the punching shear resistance is given by

v lRd,cs 0,75v lRd,c 1,5 §¨¨© d ¸¸·¹ ¨¨©§ 1 ·¹¸¸ A fsw ywd,eff sinD (11.6.52)
sr u1d

where vlRd,c is defined in Expression (11.6.47) or (11.6.50) whichever is relevant.

(2) Adjacent to the column the punching shear capacity is limited to a maximum of

ŠVEd = VEd ≤ VlRd,max ‹ (11.6.53)
u0 d

ŠThe value of vlRd,max for use in a Country may be found in its National Annex.The

recommended value is 0,4ν flcd , where v is taken equal to v1 defined in expression (11.6. .6N) ‹

11.6.5 Partially loaded areas

(1) For a uniform distribution of load on an area Ac0 (see Figure 6.29) the concentrated
resistance force may be determined as follows:

> @FRdu U ˜ ¨§ U ·¸
Ac0 ˜ flcd ˜ Ac1 / Ac0 4400 d 3,0 flcd ˜ Ac 0 © 2200 ¹ (11.6.63)

11.6.6 Fatigue

(1) For fatigue verification of elements made with lightweight aggregated concrete special
consideration is required. Reference should be made to a European Technical Approval.

11.7 Serviceability limit states

(1)P The basic ratios of span/effective depth for reinforced concrete members without axial

compression, given in 7.4.2, should be reduced by a factor K 0,15 when applied to LWAC.
E

11.8 Detailing of reinforcement - General

11.8.1 Permissible mandrel diameters for bent bars

(1) For lightweight aggregate concrete the mandrel sizes for normal density concrete given in
ˆ8.3‰ to avoid splitting of the concrete at bends, hoops and loops, should be increased by 50%.

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11.8.2 Ultimate bond stress
(1) The design value of the ultimate bond stress for bars in lightweight concrete may be
ˆcalculated using Expression 8.2, by substituting the value flctd for fctd, with flctd = flctk,0,05/JC. The‰
values for flctk,0,05 are found in Table 11.3.1.
11.9 Detailing of members and particular rules
(1) The diameter of bars embedded in LWAC should not normally exceed 32 mm. For LWAC
bundles of bars should not consist of more than two bars and the equivalent diameter should
not exceed 45 mm.
11.10 Additional rules for precast concrete elements and structures
(1) Section 10 may be applied to lightweight aggregate concrete without modifications.
11.12 Plain and lightly reinforced concrete structures
(1) Section 12 may be applied to lightweight aggregate concrete without modifications.

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SECTION 12 PLAIN AND LIGHTLY REINFORCED CONCRETE STRUCTURES

12.1 General

(1)P This section provides additional rules for plain concrete structures or where the
reinforcement provided is less than the minimum required for reinforced concrete.

Note: Headings are numbered 12 followed by the number of the corresponding main section. Headings of lower
level are numbered consecutively, without reference to subheadings in previous sections.

(2) This section applies to members, for which the effect of dynamic actions may be ignored. It
does not apply to the effects such as those from rotating machines and traffic loads. Examples
of such members include:

- members mainly subjected to compression other than that due to prestressing, e.g. walls,
columns, arches, vaults, and tunnels;

- strip and pad footings for foundations;
- retaining walls;
- piles whose diameter is t 600 mm and where NEd/Ac d 0,3fck.

(3) Where members are made with lightweight aggregate concrete with closed structure
according to Section 11 or for precast concrete elements and structures covered by this
Eurocode, the design rules should be modified accordingly.

(4) Members using plain concrete do not preclude the provision of steel reinforcement needed
to satisfy serviceability and/or durability requirements, nor reinforcement in certain parts of the
members. This reinforcement may be taken into account for the verification of local ultimate limit
states as well as for the checks of the serviceability limit states.

12.3 Materials
12.3.1 Concrete: additional design assumptions

(1) Due to the less ductile properties of plain concrete the values for Dcc,pl and Dct,pl should be
taken to be less than Dcc and Dct for reinforced concrete.

Note: The values of Dcc,pl and Dct,pl for use in a Country may be found in its National Annex. The
recommended value for both is 0,8.

(2) When tensile stresses are considered for the design resistance of plain concrete members,
the stress strain diagram (see 3.1.7) may be extended up to the tensile design strength using
Expression (3.16) or a linear relationship.

< fctd,pl = Dct,pl fctk,0,05/JC = (12.1)

(3) Fracture mechanic methods may be used provided it can be shown that they lead to the
required level of safety.

12.5 Structural analysis: ultimate limit states

(1) Since plain concrete members have limited ductility, linear analysis with redistribution or a
plastic approach to analysis, e.g. methods without an explicit check of the deformation capacity,
should not be used unless their application can be justified.

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EN 1992-1-1:2004 (E)

(2) Structural analysis may be based on the non-linear or the linear elastic theory. In the case
of a non-linear analysis (e.g. fracture mechanics) a check of the deformation capacity should be
carried out.

12.6 Ultimate limit states

12.6.1 Design resistance to bending and axial force

(1) In the case of walls, subject to the provision of adequate construction details and curing,
the imposed deformations due to temperature or shrinkage may be ignored.

(2) The stress-strain relations for plain concrete should be taken from 3.1.7.

(3) The axial resistance, NRd, of a rectangular cross-section with a uniaxial eccentricity, e, in
the direction of hw, may be taken as:

ˆNRd = Kfcd,pl u b u hw u (1-2e/hw) ‰ (12.2)

where:

ˆ Kfcd,pl is the design effective compressive strength (see 3.1.7 (3)‰
b is the overall width of the cross-section (see Figure 12.1)
hw is the overall depth of the cross-section
e is the eccentricity of NEd in the direction hw.

Note: Where other simplified methods are used they should not be less conservative than a rigorous method
using a stress-strain relationship given in 3.1.7.

NEd hw
e

b
lw

Figure 12.1: Notation for plain walls
12.6.2 Local failure
(1)P Unless measures to avoid local tensile failure of the cross-section have been taken, the
maximum eccentricity of the axial force NEd in a cross-section shall be limited to avoid large
cracks.

194

BS EN 1992-1-1:2004
EN 1992-1-1:2004 (E)

12.6.3 Shear

(1) In plain concrete members account may be taken of the concrete tensile strength in the
ultimate limit state for shear, provided that either by calculations or by experience brittle failure
can be excluded and adequate resistance can be ensured.

(2) For a section subject to a shear force VEd and a normal force NEd acting over a compressive
area Acc the absolute value of the components of design stress should be taken as:



Vcp NEd Acc (12.3)



Wcp kVEd / Acc (12.4)



Note: the value of k for use in a Country may be found in its National Annex. The recommended value is 1,5.

and the following should be checked:

Wcp d fcvd



where

ˆ if Vcp d Vc,lim fcvd f2 V f cp ctd,pl (12.5)
(12.6)
ctd,pl (12.7)



or

if Vcp ! Vc,lim fcvd f2 V fcp ctd,pl ¨§¨© V cp V c,lim ¸¹·¸ 2
2
ctd,pl



Vc,lim fcd,pl fctd ,pl fctd,pl fcd,pl



where:
fcvd is the concrete design strength in shear and compression
fcd,pl is the concrete design strength in compression
fctd,pl is concrete design strength in tension‰

(3) A concrete member may be considered to be uncracked in the ultimate limit state if either it
remains completely under compression or if the absolute value of the principal concrete tensile

ˆstress Vct1 does not exceed fctd,pl.‰

12.6.4 Torsion

(1) Cracked members should not normally be designed to resist torsional moments unless it
can be justified otherwise.

12.6.5 Ultimate limit states induced by structural deformation (buckling)
12.6.5.1 Slenderness of columns and walls

(1) The slenderness of a column or wall is given by (12.8)
O = l0/i
(12.9)
where: is the minimum radius of gyration 195
i is the effective length of the member which can be assumed to be:
l0

l0 = E ˜ lw

BS EN 1992-1-1:2004
EN 1992-1-1:2004 (E)

where:
lw clear height of the member
E coefficient which depends on the support conditions:

for columns E = 1 should in general be assumed;

for cantilever columns or walls E = 2;

for other walls E -values are given in Table 12.1.

Table 12.1: Values of E for different edge conditions

Lateral Sketch Expression Factor E
restraint A


along two B A B lw E = 1,0 for any
edges b ratio of lw/b
A
b/lw E
A
b B lw 0,2 0,26
A 0,4 0,59
0,6 0,76
A 0,8 0,85
Along three b C lw E 1 1,0 0,90
1,5 0,95
edges C ¨§ lw ·¸2 2,0 0,97
© 3b ¹ 5,0 1,00
1
b/lw E

0,2 0,10
If b t lw 0,4 0,20
0,6 0,30
E 1 0,8 0,40
1,0 0,50
Along four C 1 ¨§ lw ·¸ 2 1,5 0,69
edges © b ¹ 2,0 0,80
5,0 0,96
If b < lw

E b
2l w

A - Floor slab B - Free edge C - Transverse wall

Note: The information in Table 12.1 assumes that the wall has no openings with a height exceeding 1/3 of the
wall height lw or with an area exceeding 1/10 of the wall area. In walls laterally restrained along 3 or 4 sides with
openings exceeding these limits, the parts between the openings should be considered as laterally restrained
along 2 sides only and be designed accordingly.

(2) The E-values should be increased appropriately if the transverse bearing capacity is affected
by chases or recesses.

196